全文获取类型
收费全文 | 229篇 |
免费 | 5篇 |
专业分类
化学 | 180篇 |
晶体学 | 2篇 |
力学 | 2篇 |
数学 | 10篇 |
物理学 | 40篇 |
出版年
2024年 | 7篇 |
2022年 | 2篇 |
2021年 | 16篇 |
2020年 | 9篇 |
2019年 | 4篇 |
2018年 | 10篇 |
2017年 | 5篇 |
2016年 | 12篇 |
2015年 | 7篇 |
2014年 | 3篇 |
2013年 | 15篇 |
2012年 | 19篇 |
2011年 | 13篇 |
2010年 | 15篇 |
2009年 | 10篇 |
2008年 | 8篇 |
2007年 | 12篇 |
2006年 | 9篇 |
2005年 | 9篇 |
2004年 | 9篇 |
2003年 | 14篇 |
2002年 | 7篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有234条查询结果,搜索用时 15 毫秒
1.
Pavla Fialová Inmaculada Robina Petr Sedmera Lucie Petrásková-Hušáková 《Tetrahedron letters》2005,46(50):8715-8718
Glycosyl azides are new efficient donors for glycosidases. Their high water solubility facilitates transglycosylations with comparable or better yields than common O-glycosides. The azido group totally changes the β-GalNAc-ase/β-GlcNAc-ase ratio in β-N-acetylhexosaminidases (from the usual 0.3-1.0 to <0.01), contrary to all known aglycons. 相似文献
2.
AnaT. Carmona RichardH. Whigtman Inmaculada Robina Pierre Vogel 《Helvetica chimica acta》2003,86(9):3066-3073
Reaction of 1,4‐anhydro‐2,3,5‐tri‐O‐benzyl‐1‐deoxy‐1‐imino‐D ‐arabinitol N‐oxide ( 8 ) with allyl alcohol produced a 3.6 : 1 mixture of the two pyrrolo[1,2‐b]isoxazole derivatives 13 and 14 . The major adduct 13 was converted to 7‐deoxycasuarine ( 7 ), a potent, specific, and competitive inhibitor of amyloglucosidase from Rhizopus mold (see Table). 相似文献
3.
Shaheen Motala-Timol 《European Polymer Journal》2007,43(7):3042-3049
The synthesis of ABA triblock copolymers of the type PDMAEMA-PCL-PDMAEMA was achieved by atom transfer radical polymerization (ATRP) of DMAEMA using difunctional polycaprolactone (PCL) as macroinitiator. First, ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) was carried out in the presence of 1,2-diaminoethane/tin (II) octanoate. Dihydroxy PCL thus obtained was end-functionalized in a quantitative manner using 2-bromoisobutyryl bromide. The resulting Br-PCL-Br was used as macroinitiator in the ATRP of DMAEMA leading to triblock copolymers with PCL as the central block and PDMAEMA sequences of different lengths. NMR and SEC analyses confirmed the formation of ABA triblocks. 相似文献
4.
Local atmospheric aerosol particulate samples, collected as composites on daily 6-12 hour basis, at Quaid-i-Azam University campus, Islamabad, Pakistan, using high volume sampling technique, were analysed for Pb, Na, K, Fe, Mn, Cd, Cr, Ni, Zn and Co by FAAS method. The monitoring period ran from October, 2001 through March, 2002, with a total of 105 samples collected on cellulose filters, treated in part with the HNO3-based wet digestion method for metal quantification, and for particle size distribution separately. The metal content of the aerosols was examined in relation to dependence on meteorological parameters, such as temperature, relative humidity, wind speed, sun shine and pan evaporation. Statistical correlation analysis was conducted for multiple metal pairs in aerosols, and the data were examined in relation to meteorological parameters and relevant aerosol particle size fractions. The study revealed no viable strong correlation between the meteorological parameters and metal levels; in general, however, a significant positive correlation was found for temperature. A strong positive correlation was observed for PM<25 and PM2.5-10. For coarse particles (PM10-100 and PM>100), however, a negative correlation was observed. The levels of Na, K, Fe and Zn were found in the range of 1-5 microg/m3 while those for the rest of the metals in the sub microg/m3 range. Principal component analysis and cluster analysis were performed on dataset for source identification and appointment. Largest contribution (33%) was shown by the industrial emissions followed by traffic/road dust (16.7%). 相似文献
5.
The mixed micellar properties of a triblock copolymer, Pluronic L64, (EO)13(PO)30(EO)13, and a nonionic surfactant, Triton X-100, in aqueous solution with conventional alkyl ammonium bromides and their dimeric homologues were investigated with the help of fluorescence and cloud point measurements. The composition of mixed micelles and the interaction parameter, beta, evaluated from the critical micelle concentration (cmc) data for different mixtures using Rubingh's and Motomura's theories are discussed. It has been observed that the mixed micelle formation between monomeric/dimeric alkyl ammonium bromides and L64 was due to synergistic interactions which increase with the increase in hydrophobicity of the cationic component. On the other hand, synergistic mixing was observed in the mixed micelles of Triton X-100 and monomeric cationic surfactants, the magnitude of which decreases slightly with the increase in hydrophobicity of the cationic component. Antagonistic interactions were observed in the case of Triton X-100 and dimeric cationic surfactants. 相似文献
6.
Carmona AT Fuentes J Robina I García ER Demange R Vogel P Winters AL 《The Journal of organic chemistry》2003,68(10):3874-3883
A new route for the preparation of four new indolizidines, (1R,2S,6S,7S,8aS)- and (1R,2S,6R,7R,8aS)-1,2,6,7-tetrahydroxyindolizidine (30 and 32) and (1S,2R,7S,8S,8aR)- and (1S,2R,7R,8R,8aR)-1,2,7,8-tetrahydroxyindolizidine (44 and 46), is reported. The synthesis is based on Knoevenagel homologation of the readily available enantiomerically pure pyrrolidin-carbaldehydes 13 and 37followed by asymmetric dihydroxylation of the subsequent alkenyl pyrrolidines and cyclization of the corresponding imino-octitols. The new indolizidines and their precursors (imino-octitols 20, 25, 26) and indolizidinones 28a and 28b have been tested for inhibitory activities toward 26 glycosidases. The enzymatic inhibition of trans-7-hydroxy-d-(-)-swainsonine (44) toward alpha-mannosidases is similar to that described for trans-7-hydroxy-l-(+)-swainsonine (11b) toward naringinase (alpha-l-rhamnosidase from Penicillium decumbens). 相似文献
7.
8.
9.
Inmaculada Robina Silvia Gómez-Bujedo José G. Fernández-Bolaños José Fuentes 《合成通讯》2013,43(13):2379-2397
To prepare C-sulfonate derivatives of disaccharides two different strategies were followed. Thus 6- and 6′-C-sulfocellobiosides 4 and 10–12 were prepared starting from a suitably protected cellobioside. The 6′-C-sulfoaminocellobioside 18 was prepared by construction of the molecule through a glycosylation reaction. In both cases, the synthetic pathway involves regioselective tosylation, introduction of a sulfur atom by nucleophilic displacement with potassium thioacetate and oxidation with hydrogen peroxide. 相似文献
10.